(1) Field of the Invention
The present invention relates to a thermal printer comprising a thermal head for carrying out a printing operation, wherein the thermal head applies heat to an ink film to transfer thermally fusbile ink onto transfer or recording paper.
(2) Description of the Prior Art
A known thermal printer such as a color printer employs an ink film carrying a plurality of different color sections or frames arranged longitudinally on the ink film. The ink film, for example as shown in FIG. 2, carries a yellow frame IY, a magenta frame IM and a cyan frame C in series, and a leading position marker MP on a side of the film at a position corresponding to a leading end of each yellow ink frame IY. At the beginning of the printer operation, the ink film is advanced to a predetermined where one of the leading position markers MP is detected by a sensor. The the printing operation is started with yellow.
The type of printer that sets the position of the ink film by means of the leading position markers in advance of printing action as described above, is prone to cause certain inconvenience when power is cut off by some reasons in a printing operation and subsequently the power is turned on again to resume the printing. For example, when the power is cut off in a printing operation, the ink film and the recording paper remain in tight contact with each other at the transfer section. If the power supply is resumed in this state, the ink film cannot be taken up to set its position by means of the leading position marker. Consequently, the leading position marker cannot be detected within a predetermined time period which results in the printer giving a film empty indication. In addition, an ink film feed motor for taking up the ink film is subjected to an overload and becomes overheated under such a situation.
Known examples of thermal printer have been disclosed in U.S. Pat. Nos. 4,451,834 and 4,507,667. The former discloses a thermal printer wherein an ink film and recording paper are maintained in tight contact with each other at a transfer section and an image is printed on the recording paper by means of a thermal head. However, this patent provides no disclosure regarding means for solving the above-noted problem encountered when the power supply is commenced.
The latter patent discloses a thermal printer wherein, prior to printing a first sheet of recording paper, the ink film is advanced by a fixed amount while the thermal head is retracted from a pressure position, in order to smooth out the ink film. However, this patent again discloses nothing to solve the above-noted problem.